Proceedings of the New Zealand Society of Animal Production, 1996,
56: 125-129
Proceedings of the New Zealand Society of Animal Production, 1996,
56: 125-129
In a 17 week grazing experiment, sward surface height (SSH) was measured daily on a ryegrass/white clover sward, continuously grazed at a mean pasture height of 4.0 cm by nine yearling heifers (CA) or by nine heifers plus 27 ewe hoggets (C + S) on a ratio 1:1 W0.75. A companion rotational grazing treatment was involved.
The mean SSH was similar for CA and C+S in both grazing systems (Continuous: 4.27 vs. 4.26 cm; Rotational: 4.87 vs. 4.82 cm). The effect of species mix on sward height distribution was only significant under continuous grazing, where the proportion of the infrequently grazed heights was six times higher in CA than C+S pastures (0.30 vs. 0.05). The mean height of the ìfrequentlyî and ìinfrequentlyî grazed area was 0.5 cm (12 %) and 1.5 cm (24 %) higher in C+S than on CA pastures, respectively. Although the trends were similar in rotationally grazed treatments, neither the difference in the proportion frequently and infrequently grazed height, nor the mean sward height of these areas significantly diffrered between C+S and CA swards.
We suggest that this increase in ëgrazing heightí at the same mean SSH in continuously grazed pastures may explain some of the increase in animal performance under mixed grazing. This effect of mixed grazing was less obvious under rotational grazing.
Keywords: NZSAPAB; Cattle; co-grazing; continuous grazing; double normal distribution; dung patches; frequently grazed; infrequently grazed; pasture height; rotational grazing; and sheep.
